Multi-level trays which are capable of stacking at a first position in a like orientation and in a second position when in a 180.degree. orientation are known in the industry. Stacking trays at multiple heights allows the proper clearance for different products which may be stored in the trays. It is also advantageous for such trays to have the capability of cross-nesting when rotated in a 90.degree. orientation to reduce the space required when storing and transporting the trays when products are not stored therein.
Additionally, it is desirable for the trays to be blind stacked and unstacked. Blind stacking refers to the ability to stack a tray on top of a stack of trays, typically when the top of the stack is located overhead with respect to the handler. The tray to be stacked is generally lifted overhead and the rear of the tray is placed on the front of the stack. The tray is then pushed back along the stack until it is properly positioned on the topmost tray in the stack. Blind unstacking refers to removing the topmost tray from a stack of trays overhead. The front of the desired tray is grasped, lifted slightly, and pulled forward until it is clear of the stack at which point the tray is brought down off of the stack.
Such a multi-level bakery tray is disclosed in U.S. Pat. No. 4,960,207 issued to Tabler et al., wherein the tray has a pattern of feet along the lower edge of one end wall and corresponding recesses on the upper edge of the same end wall. A different configuration of feet and corresponding recesses are formed on the other end wall. When the trays of Tabler are stacked in a like orientation, the recesses receive the feet such that the trays are stacked in a first, low position. When the trays are in a 180.degree. orientation, the feet and recesses are misaligned and the feet are supported within a channel, providing a second, high position. However, in this high position, the feet are not positively engaged within recesses as they are in the low position, which can lead to instability of the stack.
Blind unstacking the trays of Tabler from the low position can also be problematic. As the feet are relatively long and the recesses are relatively deep, it can be difficult to free the feet at the rear of the tray from their corresponding recesses when the front of a tray is lifted in an attempt to remove the tray from the stack. One embodiment of Tabler dealing with the issue of blind unstacking discloses projections extending outwardly from the end walls which engage corresponding slots when the trays are stacked. To blind unstack a tray, it is grasped in front and lifted to a point where the projections clear the slots, and then pulled forward slightly. To allow this forward movement, the recesses must be sized larger than the feet that are received therein. The tray is then tilted back to a level position using the projection as a fulcrum about which the tray is rotated. Blind unstacking in this fashion is complex since the handler must raise the tray a sufficient distance for the projections to clear the slots but without any visual or tactile indication as to when this distance has been achieved. The construction of the tray is complex as well in order to facilitate blind unstacking in this manner.
Another multi-level bakery tray is disclosed in commonly assigned U.S. Pat. No. 5,881,902 issued to Ackermann, which is incorporated by reference fully herein. In contrast to Tabler, the tray of Ackermann includes feet and pockets on each end wall, wherein the pockets include deep pockets and shallow pockets. When trays having a like orientation are stacked, the feet of a top tray are received in the shallow pockets of a bottom tray, thereby positioning the trays in a first, high position. When the top tray is rotated 180.degree. about its vertical axis and stacked on the bottom tray, the feet of the top tray are received in the deep pockets of the bottom tray, thereby positioning the trays in a second, low position. Advantageously, the feet of the top tray are positively engaged with the pockets of the bottom tray regardless of whether the stacked trays are oriented in the high or low positions, thereby improving the stability of the stacked tray system.
Blind stacking and unstacking of the trays of Ackermann are also greatly facilitated. A drag rail extends downwardly from the bottom beneath each end wall. A shoulder is formed on each side wall proximate the ends thereof. When the rear of a tray is placed on a stack of trays, the drag rail is supported by the shoulder of the topmost tray in the stack. As the tray is pushed backwards on the stack, the feet are supported by the upper edge of the end wall until the feet reach their corresponding pockets at which point the feet slide down into and are received by the pockets. To facilitate blind unstacking, cooperating surfaces of the pockets and feet are sloped at substantially the same angle so that as the topmost tray in a stack is lifted by its front edge and pulled forward, the rearmost feet slide upwardly and forwardly out of their respective pockets until the feet reach the upper edges of the end walls at which point the tray can be slid forwardly until is free of the stack. Such sloped surfaces greatly increase the ease with which trays can be blind stacked and unstacked.
In addition to the features disclosed by Ackermann, it is desirable to have the capability to stack unlike trays together. For example, manufacturers and distributors providing different products that are stored in different types of trays prefer to be able to stack these unlike trays together in order to create a specific order for a particular retailer. The capability of stacking unlike trays in a single stack is more space efficient for storing and transporting products than if unlike trays must be placed in separate stacks. However, while the ability to stack unlike trays is advantageous, nesting of unlike trays together is generally not desired. Instead, manufacturers and distributors would prefer that different types of trays be required to be separated at the point of return shipping by the retailer, such that the manufacturer or distributor is not forced to separate much larger quantities of trays at a later time.